This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Recent genetic experiments have suggested an unprecedented speciation of iron within the mitochrondia of yeast, and in particular have provided evidence for two different pools of iron in mitochondria. This speciation effects the activity of mitochondrial superoxide dismutase (SOD), as iron from one pool is able to displace manganese from the active form of the enzyme, with the other iron pool is SOD-inert. XAS of WT and various mutant yeast mitochondria will be used to provide detailed local structural information for these two pools of mitochrondial iron.